Quantitative analysis using solids inlet probe is being done for studies of human calcium metabolism in lactation and metabolic disorders. Thermal desorption mass spectrometry of involatile organic salts has been developed for detection and identification. Mathematical modeling of calcium kinetics and quadrupole mass filters is being done. Multivariate statistical methods are being applied to large mass spectral data sets. The physiologic role and regulation of the pineal hormone melatonin is being studied in human subjects and animals. Plasma melatonin is being studied in obese children, in precociously pubescent children, and in women with breast cancer. Pineal melatonin is being measured in rodents to investigate the circadian regulation of this hormonal and its ontogeny. Estrogen and progesterone receptors are being measured in hamster uteri to study the effect of acute melatonin treatment on these receptors. The inhibitory effect of melatonin on the induction of mammary tumors in dimethylbenzathracene treated rats is being studied. In vitro production of melatonin by a single chicken pineal gland is being studied.